We report mechanistic study of the role of nitrogen in reducing aspect-ratio-dependent etching when added to a mixture of hydrocarbon and fluorocarbon gases in a magnetically enhanced reactive ion etcher. Through examination of ion and neutral transport phenomenon, reactant transport issues, and surface charging, the source of aspect-ratio-dependent etching was identified for the CHF3/CF4/Ar etch chemistry processes investigated. The total flow of CHF3 + CF4 was held constant at 30 sccm. Polymerization was found to be the primary source of aspect-ratio-dependent etching. The addition of nitrogen is investigated with respect to its impact on etch and deposition rates.